1. Field of the Invention
The invention relates to a switching module for the power section of a welding control system, and to a method for producing such a module.
In the course of development of welding control systems, increasingly high packing densities of the power electronics components are demanded, so as to keep the structural size of the tool or the like as small as possible. These higher and higher packing densities require active dissipation of lost power. For that purpose, the components are typically screwed in heat-locking fashion onto extruded hollow profile sections, through which a fluid passes, such as coolant carried in a coolant loop. Aluminum is especially suitable for the extruded hollow profile sections because of its properties, in particular its very good thermal conduction and its very good processability by means of extrusion.
2. Description of the Prior Art
German published patent disclosure DE 102 45 288 A1 shows the power section for an inverter and a method for producing the power section. FIG. 1 of the disclosure shows a schematic view of a section through the power section of the inverter. An IGBT module is mounted on a cooling body, and disk cell diodes are attached to the same cooling body. The collector of the IGBT shown is connected to the cathode of the disk cell diodes via a large-area, low-impedance copper rail. The emitter of the IGBT is connected to the anode of the disk cell diode via a further large-area, low-impedance copper rail. In the vicinity of the IGBT module, the two copper rails are separated electrically insulated from one another by means of an insulation layer. As one clearly sees in FIG. 1 of this aforementioned disclosure, the current-carrying rail is disposed directly on the cooling body. FIG. 1 shows only one-sided cooling of the disk cell diode. It is also pointed out in the disclosure that an additional cooling body can be disposed from above, to improve the utilization of the diode. Accordingly, the current supply rails would be disposed between two cooling bodies.
Similar devices are also known in conjunction with the power section of alternating current welding control systems. As a rule, two thyristor disk cells are disposed between two aluminum cooling bodies, and the current supply is again effected to the thyristor disk cells via the conductive aluminum cooling bodies. As a consequence, the cooling bodies are simultaneously used for conducting current, and thus the potential of the current supply rails is applied to these cooling bodies. Typically, the cooling bodies are connected by means of coolant hoses, so that it is possible to exchange the coolant between the cooling bodies. For that purpose, the coolant must flow into a first cooling body by means of a first coolant supply and must flow onward by means of the connection from the first to the second cooling body. The coolant flows out again at an outlet opening in the second cooling body. The connection between the cooling bodies and the inflow to and outflow from the cooling body takes place in the prior art by means of special hoses. Very high demands in terms of dielectric strength are made of these hoses, because they have to establish a connection between the first and second cooling bodies, and the cooling bodies are at different potentials. Furthermore, these hoses are also secured to the housing of the welding control system and are thus automatically connected to ground potential, since this housing is itself grounded. For connecting the hoses to a pump system, there are additional hose connections on the housing.
The disadvantage of this arrangement is that because of the potential difference that prevails between the cooling bodies as well as between the cooling bodies and the hose connections on the housing, the hoses must in principle have a certain length, so that the dielectric strength between the potentials at the power section and the ground potential is always ensured.